3D display apparatus

ABSTRACT

A display apparatus is disclosed for enabling a user to experience a 3D perception when visual information is presented by the display apparatus. The display apparatus has an image forming unit having a two-dimensional array of image subpixels arranged to emit light for presenting associated visual information, and an optical system having an array of diffractive optical elements associated with respective ones of the array of image subpixels. Each diffractive optical element is arranged to diffract light from the associated image subpixel into a diffraction pattern with a plurality of diffraction orders to provide the visual information from the associated image subpixel to a plurality of directional viewing regions associated with the plurality of diffraction orders.

CROSS REFERENCE TO RELATED APPLICATION(S)

This application is a National Phase Filing under 35 C.F.R. § 371 of andclaims priority to PCT Patent Application No. PCT/EP2016/050018, filedon Jan. 4, 2016, the content of which is hereby incorporated in itsentirety by reference.

BACKGROUND

Some embodiments relate to a display apparatus for enabling a user toexperience a 3D perception when visual information is presented by thedisplay apparatus.

Various related art display apparatuses exist for enabling a user toexperience a 3D perception when visual information is presented by thedisplay apparatus. Some related art systems may require the user to wearglasses to, for example, separate the visual information presented tothe left eye from the visual information presented to the right eye. Theinconvenience of the need to wear glasses may be overcome with so-calledautostereoscopic systems. Some systems for 3D perception use lenticularlenses to spatially direct the visual information. An example of alenticular system is described in C. van Berkel et al, “Multiview3D-LCD” published in SPIE Proceedings Vol. 2653, 1996, pages 32 to 39.

SUMMARY

Other systems use parallax barriers. Some system approaches run intotheir design limits due to physical constraints. For example, somehigh-resolution small-size display systems may require lenticular lenseswith a negative thickness. In some other systems, in particular withlarge display sizes, to allow the user to experience a high-quality 3Dperception, a display apparatus using lenticular lenses or parallaxbarriers may need a significant distance between the lenticular lensesand the display panel with the two-dimensional array of image subpixels.Further, optical tolerances may require extra mechanical measures todefine and maintain this distance, for example by using a solidtransparent plate to provide the distance, which may lead to asignificant increase in weight and cost. It would be advantageous toprovide a display apparatus with better controllable design parameters,such as thickness, weight and cost.

Some embodiments are directed to a display apparatus for enabling a userto experience a 3D perception when visual information is presented bythe display apparatus, wherein the display apparatus includes an imageforming unit that includes a two-dimensional array of image subpixelsand an optical system that includes an array of diffractive opticalelements. The two-dimensional array of image subpixels is arranged toemit light for presenting associated visual information. The array ofdiffractive optical elements is associated with respective ones of thearray of image subpixels. Each diffractive optical element is arrangedto diffract light from the associated image subpixel into a diffractionpattern including a plurality of diffraction orders to provide thevisual information from the associated image subpixel to a plurality ofdirectional viewing regions associated with the plurality of diffractionorders. The optical system thereby effectively duplicates the visualinformation presented by one subpixel to a plurality of directionalviewing regions as the visual information is provided to each of theplurality of diffraction orders, such that the user may experience a 3Dperception in each one of the plurality of directional viewing regions.The diffractive optical element may, for example, be a diffractivegrating. The diffractive optical element may be thin. The diffractiveoptical elements may provide visual information for experiencing 3Dperception without the need for additional spatial separation that maybe required in a display apparatus using conventional optics, such aslenticular lenses or parallax barriers, between the lenticular lenses orparallax barriers and the two-dimensional array if image subpixels insuch systems. The display apparatus may thereby be thinner, lighterand/or cheaper.

In an embodiment, each diffractive optical element of the array ofdiffractive optical elements is arranged to diffract light from theassociated image subpixel into the diffraction pattern including theplurality of diffraction orders according to a plurality of predefinedintensity ratios between the diffraction orders. The relativeintensities of each of the directional viewing regions may hereby bedefined to, for example, provide a higher intensity for the directionalviewing regions at the most common viewing positions, i.e., at thecentral viewing region.

In a further embodiment, the plurality of predefined intensity ratioscorresponds to a gradual variation of intensity from a central to outerdiffraction orders, the gradual variation corresponding to Lambert'scosine law, to provide the corresponding directional viewing regionswith corresponding predefined intensity ratios.

In an embodiment, the plurality of directional viewing regions arerestricted one or more predefined limited directional ranges.

For example, in an embodiment, the plurality of directional viewingregions are restricted to a predefined limited directional range. Thediffractive optical elements may be designed such that the higherdiffraction orders are suppressed. The predefined limited directionalrange may, e.g., correspond to an angular range in the horizontal planeof −60° to +60° or smaller, with 0° corresponding to the normal to thedisplay apparatus. Restricting to the predetermined limited directionalrange may allow for an increased brightness of the visual information asprovided to the plurality of directional viewing regions. The predefinedlimited directional range may, e.g., correspond to an angular range inthe horizontal plane of −30° to +30° or smaller, with 0° correspondingto the normal to the display apparatus. Restricting to the predeterminedlimited directional range may alternatively or additionally restrict theuse of the display apparatus to only the user in the predefined limiteddirectional range, and provide a reduced disturbance of other peopleand/or prevent other people to view the visual information.

In an embodiment, the plurality of directional viewing regions arerestricted to two predefined limited directional ranges. The diffractiveoptical elements may be designed such that central diffraction ordersare suppressed. The two predefined limited directional range may, e.g.,correspond to a first angular range in the horizontal plane of −45° to−15° or narrower and a second angular range in the horizontal plane of+15° to +45° or narrower, with 0° corresponding to the normal to thedisplay apparatus. Restricting to two predetermined limited directionalranges may allow two spatially separated regions wherein a user canexperience 3D perception, such as, e.g., a driver and a co-pilot in acar.

In some embodiments, each diffractive optical element is a diffractivegrating. The grating pitch and shape may be designed to provide thewanted directions and intensity ratios of the diffraction orders of thediffraction pattern of the light emitted by the associated subpixel. Thediffractive gratings may thus be arranged to provide the diffractionorders with the plurality of predefined intensity ratios.

In some embodiments, each diffractive optical element of the array ofdiffractive optical elements is arranged to diffract light from theassociated image subpixel into the diffraction pattern including theplurality of diffraction orders, wherein adjacent non-suppresseddiffraction orders of the plurality of diffraction orders associatedwith directional viewing regions are separated by one or more suppresseddiffraction orders. Thus, the diffractive optical element does notdiffract light into suppressed diffraction orders which are effectivelynot associated with respective visual information for directionalviewing regions and diffraction orders which are associated withdirectional viewing regions. For example, every third diffraction ordercould be used for repeating visual information for directional viewingregions, with every two intermediate orders suppressed. This may allowadditional design freedom for the diffractive optical element, such asadditional design freedom in pitch and shape of diffractive gratings.

In some embodiments, the array of diffractive optical elements includesa plurality of subsets of diffractive optical elements. The diffractiveoptical elements of each subset of diffractive optical elements may bearranged to provide the diffraction pattern from the associateddiffractive optical element with an associated predetermined subsetdirection. The predetermined subset directions of different subsets aredifferent to provide the visual information from the image subpixelsassociated with the different subsets to the directional viewing regionsat different directions, to enable the user to view with 3D perceptionin each of the plurality of directional viewing regions. The subsets ofdiffractive optical elements may thus provide visual information fromsubsets of associated subpixels to an associated plurality of differentdirections in each of the directional viewing regions. Each diffractiveoptical element may thus diffract the incoming light to provide thediffraction pattern, and provide the associated predetermined subsetdirection to the diffraction pattern.

In further embodiments, the diffractive optical elements of each subsetof diffractive optical elements are arranged to provide the diffractionpattern from the associated diffractive optical element with anassociated predetermined subset direction, adjacent diffraction ordersof the plurality of diffraction orders associated directional viewingregions are separated by one or more suppressed diffraction orders, andthe suppression is different for different subsets to provide thediffraction pattern from the associated diffractive optical element withthe predetermined subset direction. Each diffractive optical element maythus diffract the incoming light to provide the diffraction pattern, andprovide the associated predetermined subset direction to the diffractionpattern by suppression of diffraction orders in dependence of thepredetermined subset direction for the associated subpixel.

In some embodiments, the optical system further includes an array offurther optical elements associated with respective one or morediffractive optical elements of the array of diffractive opticalelements. The array of further optical elements includes a plurality ofsubsets of further optical elements, the further optical elements ofeach subset of further optical elements being arranged to provide thediffraction pattern from the associated one or more diffractive opticalelements with an associated predetermined subset direction. Thepredetermined subset directions of different subsets are different toprovide the visual information from the image subpixels associated withthe different subsets to the directional viewing regions at differentdirections, to enable the user to view with 3D perception in each of theplurality of directional viewing regions. The subsets of further opticalelements may thus provide visual information from subsets of associatedone or more subpixels to an associated plurality of different directionsin each of the directional viewing regions. Using further opticalelements next to the diffractive optical elements may facilitate designand/or manufacturing, and/or tolerances therein.

In some embodiments, the further optical elements of the differentsubsets of the array of further optical elements include respectivefurther diffractive components arranged to provide the associateddiffraction pattern with the corresponding predetermined subsetdirection. In some embodiments, the further diffractive opticalcomponents include, or are, blazed gratings. The blazed gratings maythus be arranged to provide the associated predetermined subsetdirection in an efficient manner.

In some embodiments, the further optical elements of the differentsubsets of the array of further optical elements include respectiverefractive optical components arranged to provide the associateddiffraction pattern with the corresponding predetermined subsetdirection. In some embodiments, the refractive optical componentsinclude, or are, prisms. The refractive optical components may thus bearranged to provide the associated predetermined subset direction in anefficient manner. The refractive optical components may be relativelyeasy to handle. The prisms may for example be provided as a prism sheet.

The further optical elements may relate one to one to a subpixels. Asingle further optical element may relate to multiple subpixels, inparticular to subpixels associated with a single full-color pixel orwith adjacent subpixels corresponding to the same subset viewingdirection.

In some embodiments, the diffractive optical elements and the furtheroptical elements may be separate elements. In alternative embodiments,the diffractive optical element and the associated further opticalelement are integrated as a single optical element. For example, inembodiments, the diffractive optical elements of each subset ofdiffractive optical elements have respective diffractive surfaces andopposite surfaces, and the respective diffractive surfaces arranged todiffract light from the associated image subpixel into the diffractionpattern including the plurality of diffraction orders are arranged at asubset-specific angle with respect to the respective opposite surfaces,where the subset-specific angle is selected to provide the associatedpredetermined subset direction. The diffractive surfaces and oppositesurfaces hereby form the refractive optical elements, integrated withthe diffractive optical elements. Each diffractive optical element maythus diffract the incoming light to provide the diffraction pattern, andprovide the associated predetermined subset direction to the diffractionpattern.

In some embodiments, the two-dimensional array of image subpixels ispositioned in between the array of further optical components and thearray of diffractive optical elements. In alternative embodiments, thearray of further optical components is positioned in between thetwo-dimensional array of image subpixels and the array of diffractiveoptical elements. In some embodiments, the array of diffractive opticalelements is positioned at a front side of the display apparatus, i.e.,the side facing a user during use.

In some embodiments, the two-dimensional image forming unit is arrangedfor emitting light with a predefined angular intensity profile from theimage subpixels of the two-dimensional array of image subpixels to theoptical system. The diffractive optical components and/or the furtheroptical components may be optimized for the predefined angular intensityprofile. The predefined angular intensity profile may, e.g., correspondto a slightly divergent beam. The predefined angular intensity profilemay relate to the profile in the direction corresponding to the assumedparallax of the user, thus in the horizontal plane. The vertical profilemay be a diffuse, Lambertian, profile or any other suitable profile.

In some embodiments, the two-dimensional image forming unit is arrangedfor emitting light with the predefined angular intensity profile with atime-periodically varying angular profile direction and to provideassociated visual information to the subpixels, to provide the visualinformation from the image subpixels associated with the differentsubsets to the directional viewing regions in periodically differentdirections, to enable the user to view with 3D perception in each of theplurality of directional viewing regions. For example, the displayapparatus may have a time-sequentially directional backlightilluminating a transmissive LCD panel. The spatial resolution if thetwo-dimensional array of image subpixels may hereby be fully used. Thenumber and/or complexity of optical components may be reduced.

In some embodiments, the array of diffractive optical elements isarranged to provide corresponding diffraction patterns for sets of imagesubpixels arranged to emit light with different colors to providecorresponding directional viewing regions associated with the pluralityof diffraction orders of light with different colors. An enhanced orimproved quality of visual information in each directional viewingregion is thereby obtained.

It will be appreciated by those of ordinary skill in the art that two ormore of the above-mentioned embodiments may be combined in any waydeemed useful. Modifications and variations of the display apparatus,that correspond to the described modifications and variations of thedisplay apparatus, can be carried out by a person of ordinary skill inthe art on the basis of the present description. Some embodiments aredefined in the independent claims. Advantageous options are defined inthe dependent claims.

BRIEF DESCRIPTION OF THE FIGURES

These and other aspects of the presently disclosed subject matter areapparent from and will be elucidated with reference to the embodimentsdescribed hereinafter. In the drawings,

FIG. 1 schematically shows a presentation of visual information by adisplay apparatus;

FIG. 2a-2d schematically show embodiments of a display apparatus;

FIG. 3-6 schematically show details of various embodiments; and

FIG. 7a-7c schematically shows details of another embodiment.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

FIG. 1 schematically shows a presentation of visual information by adisplay apparatus 140. The display apparatus 140 can enable a user toexperience a 3D perception when visual information is presented by thedisplay apparatus 140. The display apparatus 140 includes an imageforming unit 142 including a two-dimensional array of image subpixels(in later Figures shown as 142 b) and an optical system 144 including anarray of diffractive optical elements 150. The two-dimensional array ofimage subpixels is arranged to emit light for presenting associatedvisual information. The two-dimensional image forming unit 142 isarranged for emitting light with a predefined angular intensity profilefrom the image subpixels of the two-dimensional array of image subpixelsto the optical system. In the example shown, the two-dimensional imageforming unit 142 is arranged for emitting slightly divergent light. Thearray of diffractive optical elements 150 is associated with respectiveones of the array of image subpixels. Each diffractive optical elementis arranged to diffract light from the associated image subpixel into adiffraction pattern 300 including a plurality of diffraction orders toprovide the visual information from the associated image subpixel to aplurality of directional viewing regions 102, 104, 106 associated withthe plurality of diffraction orders. The image subpixels of the array ofimage subpixels are provided as image subpixels arranged to emit lightof specific colors for groups of image subpixels, such as red, green andblue light. Image subpixels may be referred to by the color of the lightthey emit, e.g., as red subpixels, green subpixels and blue subpixels.Alternative colors may be, for example, red, green, blue and yellowlight. The array of diffractive optical elements is arranged to providecorresponding diffraction patterns for sets of image subpixels arrangedto emit light with different colors to provide corresponding directionalviewing regions associated with the plurality of diffraction orders oflight with different colors. The diffractive optical elements may bediffractive gratings. The diffractive gratings associated with the imagesubpixels of the same color may have the same grating pitch. Thus, allgratings associated with red subpixels may have a first grating pitch,all gratings associated with green subpixels may have a second pitch,and all gratings associated with blue subpixels may have a third pitch,wherein the first, second and third pitch are designed to provide thepluralities of diffraction orders for light of the different colors tothe same plurality of directional viewing regions. The image subpixelsare organized in subsets of image subpixels associated with differentvisual information representing different perspective. The imagesubpixels are hereto provided with an image signal 122 from an imageprocessor 120. The image processor 120 is arranged to provide thesubpixels with drive signals to allow visual information to be presentedallowing a 3D perception. Each subset is associated with a subset ofvisual information associated with a subset direction, indicated as 0,1, 2, 3, 4 and 5, within a directional viewing region. When the user'seyes are in neighboring subsect-directions within a directional viewingregion, e.g., as indicated with 110, the user may experience a 3Dperception. The optical system may thus be said to effectively duplicatethe visual information presented by one subpixel to a plurality ofdirectional viewing regions 102, 104, 106 as the visual information isprovided to each of the plurality of diffraction orders by thediffractive optical components. The duplication is indicated with thedotted area for subset direction number 3. The user may herebyexperience a 3D perception in each one of the plurality of directionalviewing regions 102, 104, 106. In the example shown, the number ofdiffraction orders schematically shown to be limited to three, withcorresponding directional viewing regions 102, 104, 106, and apredetermined limited angular range covered by these directional viewingregions 102, 104, 106 and indicated as 100. The array of diffractiveoptical elements is arranged to diffract light from the associated imagesubpixel into the diffraction pattern including the plurality ofdiffraction orders according to a plurality of predefined intensityratios between the diffraction orders. The optical system mayeffectively duplicate the visual information presented by one subpixelto the plurality of directional viewing regions 102, 104, 106 withpredefined intensity ratios. Outer directional viewing regions, such asdirectional viewing regions 102, 106 in the example shown in FIG. 1,may, e.g., have intensity ratios according to a plurality predefinedintensity ratios between the diffraction orders.

FIG. 2a schematically shows a display apparatus 140 including an imageforming unit 142 including a backlight 142 a and a two-dimensional arrayof image subpixels 142 b, and an optical system 144 including an arrayof diffractive optical elements 150 and an array of further opticalelements 160. The array of further optical components is 160 positionedin between the two-dimensional array of image subpixels 142 b and thearray of diffractive optical elements 150, and is thereby arranged toprovide the light emitted by image subpixels of subsets of thetwo-dimensional array of image subpixels 142 b with a respective subsetdirection before the emitted light is “duplicated” by the diffractiveoptical element into the plurality of diffraction orders of thediffraction pattern. The diffractive optical element associated with asubpixel and the associated further optical element may integrated as asingle optical element.

FIG. 2b schematically shows another display apparatus 140 including animage forming unit 142 including a backlight 142 a and a two-dimensionalarray of image subpixels 142 b, and an optical system 144 including anarray of diffractive optical elements 150 and an array of furtheroptical elements 160. The two-dimensional array of image subpixels 142 bis positioned in between the array of further optical components 160 andthe array of diffractive optical elements 150 and is thereby arranged toprovide the emitted light with a respective subset direction to subsetsof the two-dimensional array of image subpixels 142 b, after which thelight is emitted by image subpixels of the subsets of thetwo-dimensional array of image subpixels 142 b with the respectivesubset direction before the light is “duplicated” by the diffractiveoptical element into the plurality of diffraction orders of thediffraction pattern.

FIG. 2c schematically shows again another display apparatus 140including an image forming unit 142 including a backlight 142 a and atwo-dimensional array of image subpixels 142 b, and an optical system144 including an array of diffractive optical elements 150 and an arrayof further optical elements 160. The array of further optical componentsis 160 and the array of diffractive optical elements 15 are positionedin between the backlight 142 a and the two-dimensional array of imagesubpixels 142 b. The array of diffractive optical elements 15 ispositioned at a close distance to the two-dimensional array of imagesubpixels 142 b. In this arrangement, the array of further opticalcomponents is 160 and the array of diffractive optical elements 15 arearranged to provide the light emitted from the backlight 142 a with arespective subset direction and to “duplicated” into the plurality ofdiffraction orders before the light is delivered to the image subpixelsof subsets of the two-dimensional array of image subpixels 142 b. Thediffractive optical element associated with a subpixel and theassociated further optical element may integrated as a single opticalelement.

FIG. 2d schematically shows again other display apparatus 140 includingan image forming unit 142 including a two-dimensional array of emissiveimage subpixels 142 c, and an optical system 144 including an array ofdiffractive optical elements 150 and an array of further opticalelements 160. The array of further optical components is 160 positionedin between the two-dimensional array of image subpixels 142 b and thearray of diffractive optical elements 150, and is thereby arranged toprovide the light emitted by image subpixels of subsets of thetwo-dimensional array of emissive image subpixels 142 c with arespective subset direction before the light is “duplicated” by thediffractive optical element into the plurality of diffraction orders ofthe diffraction pattern. The diffractive optical element associated witha subpixel and the associated further optical element may be integratedas a single optical element. The image forming unit 142 including thetwo-dimensional array of emissive image subpixels 142 c may be anorganic LED display.

FIG. 3 schematically shows a simplified embodiment of a displayapparatus 140 as shown in FIG. 2b . The display apparatus 140 includesan image forming unit 142 including a backlight 142 a and atwo-dimensional array of image subpixels 142 b, and an optical system144 including an array of diffractive optical elements 150 and an arrayof further optical elements 160. FIG. 3 schematically shows three imagesubpixels 300R1, 300L1, 300R2 together with the corresponding optics.The backlight 142 a illuminates the array of further optical elements160 with a substantially parallel beam. The two-dimensional array ofimage subpixels 142 b is positioned in between the array of furtheroptical components 160 and the array of diffractive optical elements 150and is thereby arranged to provide the light with a respective subsetdirection to subsets of the two-dimensional array of image subpixels 142b, after which the light is emitted by image subpixels of the subsets ofthe two-dimensional array of image subpixels 142 b with the respectivesubset direction before the light is “duplicated” by the diffractiveoptical element into the plurality of diffraction orders of thediffraction pattern. An array of further optical elements 160 isprovided as a prism sheet to provide the light received from thebacklight 142 a in two subset directions to the two-dimensional array ofimage subpixels 142 a. The prism sheet has a prism angle α of 3.6°. Theprisms extend along a full pixel, including or consisting of threecolored subpixels, in this example a red, green and blue subpixel. Theprism sheet is in contact with the a two-dimensional array of imagesubpixels 142 b with its prism tops. The array of diffractive opticalelements 150 includes gratings having pitches of 5.2 μm, 4.4 μm and 3.6μm for the red, green and blue subpixel respectively, to enable anoptimal 3D perception at a viewing distance of 1 m. The array ofdiffractive optical elements 150 is designed to a plurality diffractionorders corresponding to a plurality directional viewing regions ofpredetermined luminous intensity ratios.

FIG. 4 schematically shows a presentation of visual information by adisplay apparatus 140 of an exemplary embodiment of the displayapparatus 140 shown in FIG. 2a . The display apparatus 140 includes adirectional backlight 142 a and a two-dimensional array of imagesubpixels 142 b, of which three subpixels are shown. The displayapparatus 140 includes an array of diffractive optical elements 150,associated with respective ones of the array of image subpixels. Eachdiffractive optical element is arranged to diffract light from theassociated image subpixel into a diffraction pattern. The displayapparatus 140 includes an array of further optical elements 160associated with respective diffractive optical elements of the array ofdiffractive optical elements 150. The array of further optical elements160 includes a plurality of subsets of further optical elements. Thefurther optical elements of each subset of further optical elements arearranged to provide the diffraction pattern from the associated one ormore diffractive optical elements with an associated predeterminedsubset direction. The predetermined subset directions of differentsubsets are different to provide the visual information from the imagesubpixels associated with the different subsets to the directionalviewing regions at different directions, to enable the user to view with3D perception in each of the plurality of directional viewing regions.The further optical elements of the different subsets of the array offurther optical elements 160 include respective further diffractivecomponents arranged to provide the associated diffraction pattern withthe corresponding predetermined subset direction. In the example shown,the further diffractive optical components are blazed gratings, arrangedto provide the corresponding predetermined subset direction. FIG. 4schematically shows three subpixels of the array of image subpixels. Thethree subpixels belong to three different subsets, corresponding tosubset directions 2, 3 and 4 (refer to FIG. 1). The further diffractiveoptical components 160 provide the light emitted from the associatedsubpixels 142 b with a subset direction and then emit the light to theassociated diffractive optical element 150. As indicated, the threefurther diffractive optical components 160 shown each provide adifferent subset direction to the emitted light. The further diffractivecomponents 160 associated with subpixels of the same subset and arrangedto emit light of different colors are designed to provide equal subsetdirections. Each diffractive optical element 150 diffract lights fromthe associated image subpixel into a diffraction pattern including aplurality of diffraction orders indicated as −1, 0, 1, to provide thevisual information from the associated image subpixel to a plurality ofdirectional viewing regions 102, 104, 106 associated with the pluralityof diffraction orders.

FIG. 5 schematically shows details of another embodiment. The embodimentof FIG. 5 differs from the embodiment of FIG. 4 at least in that thefurther optical elements 160 are not further diffractive opticalcomponents but refractive optical components arranged to provide theassociated diffraction pattern with the corresponding predeterminedsubset direction. In the example shown, the refractive opticalcomponents are prisms, arranged to provide the correspondingpredetermined subset direction. Thus, the refractive optical components160 provide the light emitted from the associated subpixels 142 b with asubset direction and then emit the light to the associated diffractiveoptical element 150. Each diffractive optical element 150 diffractslight from the associated image subpixel into a diffraction patternincluding a plurality of diffraction orders indicated as −1, 0, 1, toprovide the visual information from the associated image subpixel to aplurality of directional viewing regions 102, 104, 106 associated withthe plurality of diffraction orders.

FIG. 6 schematically shows details of again another embodiment. In theembodiment shown in FIG. 6, the array of diffractive optical elements151 is arranged to diffract light from the associated image subpixelinto the diffraction pattern including the plurality of diffractionorders, wherein adjacent non-suppressed diffraction orders of theplurality of diffraction orders associated directional viewing regionsare separated by one or more suppressed diffraction orders. In theschematic example of FIG. 6, five adjacent diffraction orders aresuppressed and one out of six diffraction orders is used for visualinformation, where the suppression is dependent on the viewing directionassociated with a subpixel. FIG. 6 shows the selective suppression in aschematic manner: three subpixels are associated with directionslabelled 2, 3 and 4; the left diffractive optical element 151 isdesigned to diffract light from the associated image subpixel into adiffraction pattern including a plurality of diffraction ordersindicated as −7, −1, 5 to provide the visual information from theassociated image subpixel to a plurality of directional viewing regions102, 104, 106 associated with the plurality of diffraction orders; themiddle diffractive optical element 151 is designed to diffract lightfrom the associated image subpixel into a diffraction pattern includinga plurality of diffraction orders indicated as −6, 0, 6 to provide thevisual information from the associated image subpixel to a plurality ofdirectional viewing regions 102, 104, 106 associated with the pluralityof diffraction orders; and the left diffractive optical element 151 isdesigned to diffract light from the associated image subpixel into adiffraction pattern including a plurality of diffraction ordersindicated as −5, −1, 7 to provide the visual information from theassociated image subpixel to a plurality of directional viewing regions102, 104, 106 associated with the plurality of diffraction orders. Thediffractive optical elements of each subset of diffractive opticalelements is thus arranged to provide the diffraction pattern from theassociated diffractive optical element with an associated predeterminedsubset direction, with the predetermined subset directions of differentsubsets being different to provide the visual information from the imagesubpixels associated with the different subsets to the directionalviewing regions at different directions, to enable the user to view with3D perception in each of the plurality of directional viewing regions.The suppression is different for different subsets to provide thediffraction pattern from the associated diffractive optical element withthe predetermined subset direction.

FIG. 7a-7c schematically shows details of again another embodiment. Thedisplay apparatus 140 shown on FIG. 7a-7c includes a time-sequentialdirectional backlight 142 aS and a two-dimensional array of imagesubpixels 142 b, of which three subpixels are shown. The displayapparatus 140 includes an array of diffractive optical elements 150,associated with respective ones of the array of image subpixels. Eachdiffractive optical element is arranged to diffract light from theassociated image subpixel into a diffraction pattern. In the exampleshown, each diffractive optical element diffracts light into adiffraction pattern of three orders, −1, 0 and 1, and any other othersare suppressed. The diffractive optical components thus provide thevisual information from the associated image subpixel to a plurality ofdirectional viewing regions 102, 104, 106 associated with the pluralityof diffraction orders. The two-dimensional image forming unit 142 isarranged for emitting light with the predefined angular intensityprofile with a time-periodically varying angular profile direction andto provide associated visual information to the subpixels 142 b toprovide the visual information from the image subpixels associated withthe different subsets to the directional viewing regions in periodicallydifferent directions, to enable the user to view with 3D perception ineach of the plurality of directional viewing regions.

FIG. 7a-7c show three successive moments in time. In FIG. 7a , thetime-sequential directional backlight 142 aS emits lights with a firstpredefined angular intensity profile having a first profile directionassociated with viewing direction 2; in FIG. 7b , the time-sequentialdirectional backlight 142 aS emits lights with a second predefinedangular intensity profile having a second profile direction associatedwith viewing direction 3, substantially perpendicular to the screen; inFIG. 7c , the time-sequential directional backlight 142 aS emits lightswith a third predefined angular intensity profile having a third profiledirection associated with viewing direction 4. The viewing directionsassociated with the different profile directions are different toprovide the visual information from the image subpixels associated withthe different profile directions to the directional viewing regions atdifferent directions, to enable the user to view with 3D perception ineach of the plurality of directional viewing regions.

It should be noted that the above-mentioned embodiments illustraterather than limit the presently disclosed subject matter, and that thoseof ordinary skill in the art will be able to design many alternativeembodiments without departing from the scope of the appended claims. Inthe claims, any reference signs placed between parentheses shall not beconstrued as limiting the claim. Use of the verb “include” and itsconjugations does not exclude the presence of elements or steps otherthan those stated in a claim. The article “a” or “an” preceding anelement does not exclude the presence of a plurality of such elements.Some embodiments may be implemented by hardware including severaldistinct elements, and by a suitably programmed computer. In the deviceclaim enumerating several methods, several of these methods may beembodied by one and the same item of hardware. The mere fact thatcertain measures are recited in mutually different dependent claims doesnot indicate that a combination of these measures cannot be used toadvantage.

The invention claimed is:
 1. A display apparatus for enabling a user toexperience a 3D perception in a plurality of directional viewing regionswhen visual information is presented by the display apparatus, thedisplay apparatus comprising: an image forming unit that includes atwo-dimensional array of image subpixels arranged to emit light forpresenting associated visual information, and an optical system thatincludes an array of first diffractive optical elements associated withrespective ones of the array of image subpixels, each first diffractiveoptical element being arranged to diffract light from the associatedimage subpixel into a diffraction pattern including a plurality ofdiffraction orders to provide the visual information from the associatedimage subpixel to a plurality of directional viewing regions associatedwith the plurality of diffraction orders, so as to effectively duplicatethe visual information presented by the associated subpixel to each ofthe plurality of directional viewing regions, the optical system furtherincluding an array of second diffractive optical elements associatedwith respective one or more first diffractive optical elements of thearray of first diffractive optical elements, the array of seconddiffractive optical elements including a plurality of subsets of seconddiffractive optical elements, the second diffractive optical elements ofeach subset being arranged to provide the diffraction patterns with anassociated predetermined subset direction, the predetermined subsetdirections of different subsets of second diffractive optical elementsbeing different so as to enable separation of visual information to bepresented to the left eye of the user from visual information to bepresented to the right eye of the user to enable the user to view with3D perception, the array of first diffractive optical elements thusbeing arranged to provide the visual information from the imagesubpixels associated with the second diffractive optical elements of thedifferent subsets to each of the directional viewing regions at theassociated predetermined different subset directions within each of theplurality of directional viewing regions associated with the pluralityof diffraction orders so as to enable the user to view with 3Dperception in each of the plurality of directional viewing regions. 2.The display apparatus according to claim 1, wherein each firstdiffractive optical element of the array of first diffractive opticalelements is arranged to diffract light from the associated imagesubpixel into the diffraction pattern including the plurality ofdiffraction orders, wherein adjacent non-suppressed diffraction ordersof the plurality of diffraction orders associated with the directionalviewing regions are separated by one or more suppressed diffractionorders.
 3. The display apparatus according to claim 2, wherein eachfirst diffractive optical element of the array of first diffractiveoptical elements is arranged to diffract light from the associated imagesubpixel into the diffraction pattern including the plurality ofdiffraction orders according to a plurality of predefined intensityratios between the diffraction orders.
 4. The display apparatusaccording to claim 2, wherein the plurality of directional viewingregions are restricted to one or more predefined limited directionalranges.
 5. The display apparatus according to claim 2, wherein eachdiffractive optical element is a diffractive grating.
 6. The displayapparatus according to claim 2, the two-dimensional image forming unitbeing arranged for emitting light with a predefined angular intensityprofile from the image subpixels of the two-dimensional array of imagesubpixels to the optical system.
 7. The display apparatus according toclaim 1, wherein each first diffractive optical element of the array offirst diffractive optical elements is arranged to diffract light fromthe associated image subpixel into the diffraction pattern including theplurality of diffraction orders according to a plurality of predefinedintensity ratios between the diffraction orders.
 8. The displayapparatus according to claim 7, wherein the plurality of directionalviewing regions are restricted to one or more predefined limiteddirectional ranges.
 9. The display apparatus according to claim 7,wherein each diffractive optical element is a diffractive grating. 10.The display apparatus according to claim 1, wherein the plurality ofdirectional viewing regions are restricted to one or more predefinedlimited directional ranges.
 11. The display apparatus according to claim10, wherein each diffractive optical element is a diffractive grating.12. The display apparatus according to claim 1, wherein each firstdiffractive optical element is a diffractive grating.
 13. The displayapparatus according to claim 1, the two-dimensional image forming unitbeing arranged for emitting light with a predefined angular intensityprofile from the image subpixels of the two-dimensional array of imagesubpixels to the optical system.
 14. The display apparatus according toclaim 13, the two-dimensional image forming unit being arranged foremitting light with the predefined angular intensity profile with atime-periodically varying angular profile direction and to provideassociated visual information to the subpixels to provide the visualinformation from the image subpixels associated with the differentsubsets to the directional viewing regions in periodically differentdirections, to enable the user to view with 3D perception in each of theplurality of directional viewing regions.
 15. The display apparatusaccording to claim 1, the array of first diffractive optical elementsbeing arranged to provide corresponding diffraction patterns for sets ofimage subpixels arranged to emit light with different colors to providecorresponding directional viewing regions associated with the pluralityof diffraction orders of light with different colors.